Semiconductor Chip that Emits Polarized Radiation

ABSTRACT

A semiconductor chip that emits radiation includes a semiconductor body having an active zone, which emits unpolarized radiation having a first radiation component of a first polarization and having a second radiation component of a second polarization. A lattice structure acts as a waveplate or polarization filter and causes an increase in one radiation component relative to the other radiation component in the radiation emitted by the semiconductor chip through an output side. Therefore, the semiconductor chip emits polarized radiation, which has the polarization of the amplified radiation component. The attenuated radiation component remains in the semiconductor chip an optical structure, which converts the polarization of at least part of the attenuated radiation component remaining in the semiconductor chip to the polarization of the amplified radiation component, and a reflective rear side opposite the output side.

This patent application is a national phase filing under section 371 ofPCT/EP2012/056910, filed Apr. 16, 2012, which claims the priority ofGerman patent application 10 2011 017 196.7, filed Apr. 15, 2011, eachof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the invention relate to a semiconductor chip that emitspolarized radiation.

BACKGROUND

Radiation-emitting semiconductor chips are advantageous light sourcesowing to their compact size and efficiency. However, on account ofspontaneous emission the radiation generated is usually nondirectionaland unpolarized. However, for applications such as LCD backlighting, forexample, light sources that emit polarized radiation are advantageous.

Both German Patent Publication No. DE 10 2007 062 041 and U.S. PatentPublication No. 2008/0035944 describe radiation-emitting semiconductorchips that emit polarized radiation. Furthermore, they describe that theradiation component which cannot couple out of the semiconductor chip onaccount of its polarization is at least partly recovered in thesemiconductor chip by photon recycling.

SUMMARY OF THE INVENTION

Embodiments of the invention specify a radiation-emitting semiconductorchip that generates polarized radiation in an efficient manner.

In accordance with one embodiment, the radiation-emitting semiconductorchip comprises a semiconductor body comprising an active zone, whichemits unpolarized radiation having a first radiation component of afirst polarization and having a second radiation component of a secondpolarization. Furthermore, the radiation-emitting semiconductor chipcomprises a grating structure, which acts as a wave plate orpolarization filter and brings about an increase in one radiationcomponent relative to the other radiation component in the radiationemitted by the semiconductor chip through a coupling-out side, such thatthe semiconductor chip emits polarized radiation having the polarizationof the amplified radiation component, wherein the attenuated radiationcomponent remains in the semiconductor chip. Furthermore, theradiation-emitting semiconductor chip comprises an optical structure,which converts the polarization of at least part of the attenuatedradiation component remaining in the semiconductor chip into thepolarization of the amplified radiation component. Furthermore, areflective rear side is arranged opposite the coupling-out side.

In addition to absorption and reemission processes in the active zone,therefore, the radiation component which remains in the semiconductorchip and which cannot couple out of the semiconductor chip on account ofits polarization can be recovered by the change of the polarization bymeans of the optical structure.

In one configuration of the radiation-emitting semiconductor chip, thegrating structure, which is provided for increasing one radiationcomponent relative to the other radiation component in the radiationemitted by the semiconductor chip through a coupling-out side, comprisesa plurality of alternately arranged first grating regions of a firstmaterial and second grating regions of a second material. In particular,the grating regions of the same material are at a distance from oneanother which is smaller than a wavelength of the radiation generated bythe active zone. Preferably, the distance is chosen such that thegrating structure loses its diffraction properties. As a result, thegrating structure behaves like a homogeneous medium having a uniformrefractive index.

In accordance with one preferred development, the first and secondgrating regions are embodied in strip-type fashion and are arrangedparallel to one another. The width of the first and second gratingregions should make up a fraction of the distance at which the gratingregions of the same material succeed one another. Such small structurescan be produced, for example, by lithographic techniques such asholographic lithography or a nanoimprint method.

In accordance with a first variant, the grating structure acts as awaveplate. In particular, the grating structure in this case correspondsto a birefringent medium. In this case, the radiation component which ispolarized parallel to the strip-type grating regions experiences adifferent effective refractive index than the radiation component whichis polarized perpendicular to the strip-type grating regions.Preferably, the first radiation component experiences a different phaseshift than the second radiation component upon transmission through thegrating structure. By way of example, the thickness of the gratingstructure can be chosen such that the first radiation component, uponpassing through the waveplate twice, experiences a phase shift of π(pi), while the second radiation component experiences a phase shiftdifferent than π.

Preferably, the grating structure acting as a waveplate is arrangedbetween the active zone and the reflective rear side of thesemiconductor chip. When setting a suitable distance between the activezone and the reflective rear side, account is taken of the total phaseshift which the radiation emitted by the active zone and reflected atthe rear side experiences between the active zone and the rear side. Thedistance between the active zone and the reflective rear side is set, inparticular, in such a way that as a result of interference of radiationof the same polarization, one radiation component is amplified and theother radiation component is attenuated. By way of example, the distanceis set in such a way that the first radiation component interferesconstructively in the case of a phase shift of π, while the secondradiation component interferes destructively.

In accordance with one preferred variant, the first radiation componentis polarized perpendicular to the strip-type grating regions.Furthermore, the second radiation component is polarized parallel to thestrip-type grating regions.

Advantageously, the perpendicularly polarized radiation component isemitted in a perpendicular direction, that is to say perpendicularly tothe coupling-out side, while the parallel polarized radiation componentis emitted in a horizontal direction, that is to say parallel to thecoupling-out side.

Consequently, the semiconductor chip in this variant emitsperpendicularly polarized radiation.

In accordance with one preferred embodiment, the first or second gratingregions of the grating structure acting as a waveplate are formed from amaterial that is transmissive to the radiation generated in the activezone. For example, the first or second grating regions can be formedfrom SiO₂, GaAs, AlGaAs, InGaAlP or GaN.

Preferably, the first grating regions are produced by etching a surfaceof the semiconductor body, such that they are formed from thesemiconductor material of the semiconductor body. The second gratingregions are gas-filled, in particular air-filled, interspaces betweenthe first grating regions. Some other transparent filling material, forexample, a TCO (Transparent Conductive Oxide) is also conceivable forthe second grating regions.

In accordance with a second variant, the grating structure acts as apolarization filter. Preferably, one radiation component is transmittedat the grating structure acting as a polarization filter, and the otherradiation component is reflected.

In particular, the first grating regions of the grating structurecontain or consist of a metal. The second grating regions can be forexample gas-filled, in particular air-filled, interspaces between thefirst grating regions. By means of the strip-type grating regions thatcontain or consist of a metal, the radiation component which is parallelpolarized is reflected, while the radiation component which isperpendicularly polarized is transmitted.

The first radiation component can be, in particular, perpendicularlypolarized, while the second radiation component is parallel polarized.

In accordance with one preferred embodiment, the grating structureacting as a polarization filter is arranged on a surface of thesemiconductor body that is on the coupling-out side. In this embodiment,the optical structure is advantageously arranged between that surface ofthe semiconductor body which is on the coupling-out side and thepolarization filter. In particular, the optical structure is in thiscase embodied as a waveplate.

Alternatively, the grating structure acting as a polarization filter canalso be arranged between the active zone and the reflective rear side.In this case, in particular, the parallel polarized radiation componentis reflected by the grating structure, while the perpendicularlypolarized radiation component is transmitted and reflected by thereflective rear side. If the parallel polarized radiation component isintended to be amplified, in particular the distance between active zoneand grating structure is set in such a way that the parallel polarizedradiation component interferes constructively. If the perpendicularlypolarized radiation component is intended to be amplified, in particularthe distance between active zone and reflective rear side is set in sucha way that the perpendicularly polarized radiation component interferesconstructively.

In one preferred configuration, the grating structure acting as apolarization filter is a contact structure serving for currentspreading. In this case, the grating structure is preferably arranged atthe coupling-out side of the semiconductor chip, such that the gratingstructure can be directly electrically contact-connected externally, forexample, by means of a contact wire.

The optical structure provided for changing the polarization of theradiation component remaining in the semiconductor chip can be awaveplate, like the grating structure. Furthermore, the opticalstructure can be a randomly roughened structure or else a predefinedstructure.

The optical structure is arranged in particular within the semiconductorchip between the coupling-out side and the rear side.

In accordance with one preferred embodiment, the optical structurecomprises structured regions extending in a plane arranged parallel to aplane in which the grating structure extends, wherein the structuredregions run transversely with respect to the grating regions of thegrating structure. The structured regions are therefore not arrangedparallel to the grating regions. The structured regions form with thegrating regions an angle of greater than 0° and less than 90°.Preferably, the angle is 45°. In this case, the radiation componentwhich remains in the semiconductor chip and which is reflected by thestructured regions experiences, in particular, a rotation of thepolarization by 90°. Preferably, the structured regions are arranged atleast partly parallel to one another.

By way of example, it is possible to embody the optical structure in themanner of the waveplate like a birefringent medium with alternatelyarranged structured regions having different refractive indexes.Furthermore, the structured regions can be depressions introduced into asemiconductor layer of the semiconductor body. The depressions can begas-filled, in particular air-filled.

In accordance with a further advantageous embodiment, the opticalstructure comprises structured regions having oblique side faces whichrun at an angle of greater than 0° and less than 90°, obliquely withrespect to a plane in which the grating structure extends. Preferably,the angle is 45°. The radiation component which remains in thesemiconductor chip experiences, in particular, a rotation of thepolarization by 90° upon reflection at two opposite side faces of twoadjacent structured regions. Preferably, the structured regions areembodied as prisms or pyramids. These can be etched, for example, into asemiconductor layer of the semiconductor chip.

In one preferred configuration, the reflective rear side is providedwith the optical structure. By way of example, in this case, a rear-sidesurface of the semiconductor body can be provided with the opticalstructure and coated with a reflection layer, such that a reflectiverear side having an optical structure is formed as a consequence.

BRIEF DESCRIPTION OF THE DRAWINGS

The radiation-emitting semiconductor chip described here is explained ingreater detail below on the basis of exemplary embodiments and theassociated figures.

FIG. 1A shows, in a schematic cross-sectional view, a first exemplaryembodiment of the radiation-emitting semiconductor chip describedherein;

FIG. 1B shows a perspective enlarged view of the grating structurecontained in FIG. 1A;

FIGS. 2A and 2B show graphs with values for the effective refractiveindex and the thickness of a grating structure;

FIG. 3A shows, in a schematic cross-sectional view, a second exemplaryembodiment of the radiation-emitting semiconductor chip describedherein;

FIG. 3B shows a schematic plan view of the grating structure containedin FIG. 3A;

FIG. 4 shows, in a schematic cross-sectional view, a third exemplaryembodiment of the radiation-emitting semiconductor chip describedherein; and

FIGS. 5A, 5B, 6, 7, 8A and 8B show further exemplary embodiments of theoptical structure described herein.

Elements that are identical, of identical type or act identically areprovided with the same reference signs in the figures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The first exemplary embodiment of a radiation-emitting semiconductorchip 1 as illustrated in FIG. 1A comprises a semiconductor body 2comprising a plurality of layers formed from a semiconductor material.The semiconductor material can be a nitride- or arsenide-based compoundsemiconductor, which in the present case means that at least one layercontains Al_(n)Ga_(m)In_(1−n−m)N or Al_(n)Ga_(m)In_(1−n−m)As, where0≦n≦1, 0≦m≦1 and n+m≦1. In particular, the semiconductor chip 1 is athin-film semiconductor chip, that is to say that a growth substrateused for producing the semiconductor body 2 is detached or at leastgreatly thinned.

For the purpose of generating radiation, the semiconductor body 2comprises an active zone 3. The active zone 3 comprises a pn junction,which in the simplest case is formed from a p-conducting and ann-conducting semiconductor layer, which directly adjoin one another.Preferably, the actual radiation-generating layer, for instance in theform of a doped or undoped quantum layer, is formed between thep-conducting and n-conducting semiconductor layers. The quantum layercan be shaped as a single quantum well (SQW) structure or multiplequantum well (MQW) structure or else as a quantum wire or quantum dotstructure. The active zone 3 emits unpolarized radiation having a firstradiation component S1 of a first polarization and having a secondradiation component S2 of a second polarization.

In order to increase one radiation component S1, S2 relative to theother radiation component S2, S1 in the radiation S emitted by thesemiconductor chip 1 through a coupling-out side 6, the semiconductorchip 1 comprises a grating structure 4. In this exemplary embodiment,the grating structure 4 acts as a waveplate. In this case, for the firstradiation component S1 upon transmission through the grating structure 4acting as a waveplate it is possible to obtain a different phase shiftthan for the second radiation component S2.

The grating structure 4 is arranged between the active zone 3 and areflective rear side 7. The radiation components emitted in thedirection of the reflective rear side 7 therefore pass through thegrating structure 4 twice before they reach the coupling-out side 6.

A distance d between the active zone and the reflective rear side 7 isset in such a way that the total phase shift brought about by thedistance d and the grating structure 4 leads to constructiveinterference for one radiation component S1, S2 and to destructiveinterference for the other radiation component S2, S1, such that oneradiation component S1, S2 is amplified and the other radiationcomponent S2, S1 is attenuated. In particular, the grating structure 4is a λ/4 plate that leads to a phase shift of π for the first radiationcomponent S1. Preferably, the distance d is set in such a way that thefirst radiation component S1 is amplified and the second radiationcomponent S2 is attenuated. Furthermore, the first radiation componentS1 is, in particular, perpendicularly polarized and has a main emissiondirection in a perpendicular direction, that is to say perpendicularlyto the coupling-out side 6. By contrast, the second radiation componentS2 is, in particular, parallel polarized and has a main emissiondirection in a horizontal direction, that is to say parallel to thecoupling-out side 6. Consequently, the radiation S emitted by thesemiconductor chip 1 is substantially perpendicularly polarized.

In order to change the polarization of at least part of the attenuatedradiation component S2, S1 remaining in the semiconductor chip 1 intothe polarization of the amplified radiation component S1, S2, thesemiconductor chip 1 comprises an optical structure 5. In the exemplaryembodiment illustrated in FIG. 1A, the optical structure 5 is a randomlyroughened structure. The optical structure 5 can be produced, forexample, by etching a semiconductor layer of the semiconductor body 2.Such an optical structure 5 can be situated, as illustrated, within thesemiconductor chip 1, or else at a surface of the semiconductor chip 1.

The properties of the grating structure 4 illustrated in FIG. 1A will beexplained in greater detail in association with FIGS. 1B, 2A and 2B.

As is illustrated in FIG. 1B, the grating structure 4 comprises aplurality of alternately arranged first grating regions 4 a and secondgrating regions 4 b. The first grating regions 4 a are formed from adifferent material than the second grating regions 4 b and have adifferent refractive index. Both grating regions 4 a, 4 b advantageouslycontain a radiation-transmissive material. In particular, the firstgrating regions 4 a are formed from the semiconductor material of thesemiconductor body 2, for example GaN or GaAs. The second gratingregions 4 b are interspaces between the first grating regions 4 b andcan be gas-filled, for example, air-filled, or contain aradiation-transmissive oxide such as SiO₂ or a TCO.

In the exemplary embodiment illustrated, the first grating regions 4 aare embodied in strip-type fashion. A distance a between two successivefirst grating regions 4 a is smaller than a wavelength of the radiationemitted by the active zone 3. Likewise, a width b of the first gratingregions 4 a is smaller than the wavelength of the radiation emitted bythe active zone 3. Preferably, the same correspondingly applies to thesecond grating regions 4 b. As a result of the small distance a, thegrating structure 4 loses its diffraction properties and behaves like ahomogeneous medium having a uniform refractive index.

One property of the grating structure 4 illustrated is that radiationwhich is polarized parallel to the grating regions 4 a, 4 b experiencesa different effective refractive index than radiation which is polarizedperpendicularly to the grating regions 4 a, 4 b. The grating structure 4has birefringent properties.

The graph in FIG. 2A illustrates in curve 1 calculated values for theeffective refractive index ne of a possible grating structure in adirection parallel to the grating regions and in curve 2 calculatedvalues for the effective refractive index ne of the grating structure ina direction perpendicular to the grating regions. Curve 3 represents thedifference between the two curves 1 and 2. The values for the effectiverefractive index ne are indicated as a function of a variable C, whichindicates the ratio of the width b of a first grating region to thedistance a between two successive first grating regions. If the width band the distance a are of the same magnitude (C=0), then the gratingstructure undergoes transition to an unstructured homogeneous mediumformed from a single material. In the exemplary embodiment in FIG. 2A,the first grating regions are formed from GaAs having a refractive indexof 3.5. The second grating regions are air-filled interspaces. For C=0,the effective refractive index ne corresponds to the refractive index ofthe first grating regions, that is to say to the refractive index ofGaAs.

For C=1, the effective refractive index ne corresponds to the refractiveindex of the second grating regions, namely to the refractive index ofair. In the case of C=0.33, a maximum difference arises between theeffective refractive indexes ne parallel and perpendicular to thegrating regions. The two values nopt for the effective refractiveindexes ne are taken as a basis for the calculation of a suitablethickness for the grating structure.

The graph in FIG. 2B shows calculated values for the thickness h of thegrating structure as a function of the variable C. For a desired phaseshift of π for perpendicularly polarized radiation having a wavelengthof 1,000 nm, a thickness of h≈0.2 μm arises in the case of C=0.33.

FIG. 3A illustrates a second exemplary embodiment of aradiation-emitting semiconductor chip 1 comprising elementscorresponding to the first exemplary embodiment. In contrast to thefirst exemplary embodiment, the grating structure 4 acts as apolarization filter. In this case, one radiation component S1, S2 istransmitted at the grating structure 4 and the other radiation componentS2, S1 is reflected.

In accordance with the second exemplary embodiment, the gratingstructure 4 comprises first grating regions 4 a, which contain a metalor consist thereof. In particular, the first grating regions 4 a can beformed from gold. The second grating regions 4 b are interspaces betweenthe first grating regions 4 a and are gas-filled, in particularair-filled. The first grating regions 4 a are embodied in strip-typefashion. By means of the strip-type first grating regions 4 a, theradiation component S2 that is parallel polarized is reflected, whilethe radiation component S1 that is perpendicularly polarized istransmitted.

At a wavelength of 1,000 nm, the distance between the first gratingregions 4 a is advantageously 200 nm. An advantageous width of the firstgrating regions 4 a is 60 nm in this case.

The grating structure 4 is applied on a surface 10 of the semiconductorbody 2 that is on the coupling-out side. The optical structure 5 isarranged on a side of the active zone 3 situated opposite the gratingstructure 4. Alternatively, the optical structure 5 can be arrangedbetween that surface 10 of the semiconductor body 2 which is on thecoupling-out side and the grating structure 4.

In the second exemplary embodiment, the optical structure 5 is embodiedin the manner of a waveplate corresponding to a birefringent mediumhaving alternately arranged structured regions having differentrefractive indexes (not illustrated). The structured regions areembodied, in particular, in a strip-type fashion. The structured regionsfurthermore advantageously extend in a plane arranged parallel to aplane in which the grating structure 4 extends, wherein the structuredregions run transversely with respect to the grating regions 4 a andform therewith an angle of greater than 0° and less than 90°, preferablyof 45°. As a result, the polarization of the parallel polarizedradiation component S2 reflected at the grating structure 4 can berotated in particular by 90°. The radiation component having the rotatedpolarization is then perpendicularly polarized and can couple out fromthe semiconductor chip 1.

The grating structure 4 arranged on a surface 10 on the coupling-outside in the second exemplary embodiment simultaneously serves as acontact structure. As shown by FIG. 3B in a plan view of thesemiconductor chip, the grating structure 4 is provided with a contactpad 8 and contact arms 9, which connect the first grating regions 4 a toone another. By means of the contact arms 9, the first grating regions 4a can be supplied with current and distribute the current over theentire surface on the coupling-out side.

FIG. 4 shows a third exemplary embodiment of a radiation-emittingsemiconductor chip 1. In this case, the reflective rear side 7 isprovided with the optical structure 5. The optical structure 5 comprisesjag-like structured regions 5 a suitable for at least partly convertingthe polarization of the impinging second radiation component S2, whichis reflected at the grating structure 4, into the polarization of thefirst radiation component S1, such that coupling out of thesemiconductor chip 1 is possible. For producing the optical structure 5,a rear-side surface of the semiconductor body 2 can be structured andprovided with a reflective coating.

FIG. 5A shows a further exemplary embodiment of an optical structure 5in a plan view of the semiconductor chip 1. The structured regions 5 aare depressions, in particular in the form of elongated trenches, whichrun parallel to one another. Preferably, the depressions are etched intoa rear-side surface of the semiconductor body 2 (cf. FIG. 5B). Thestructured regions 5 a extend in a plane arranged parallel to a plane inwhich the grating structure 4 extends, wherein the structured regions 5a run transversely with respect to the grating regions 4 a and formtherewith an angle α of greater than 0° and less than 90°, preferably of45°. In this exemplary embodiment, the structured regions 5 a haveinclined side faces 11, wherein the side faces 11 run obliquely withrespect to the plane in which the grating structure 4 extends.

Further exemplary embodiments of an optical structure 5 are shown byFIGS. 6 and 7 in a plan view of the semiconductor chip. In this case,the optical structure 5 comprises a plurality of parallel runningstructured regions 5 a of a first orientation and a plurality ofparallel running structured regions 5 a of a second orientation. Thestructured regions 5 a of the first orientation run transversely, inparticular perpendicularly, with respect to the structured regions 5 aof the second orientation. The first grating regions 4 a form an angle αof greater than 0° and less than 90°, preferably of 45°, both with thestructured regions 5 a of the first orientation and with the structuredregions 5 a of the second orientation. The structured regions 5 a areembodied as depressions, in particular in the form of elongatedtrenches. In the exemplary embodiment in FIG. 6, the depressions haveinterruptions. The depressions of the second orientation run through theinterruptions of the depressions of the first orientation. In theexemplary embodiment in FIG. 7, the depressions are continuous, suchthat the depressions of the first orientation and the depressions of thesecond orientation intersect.

FIG. 8A shows a further exemplary embodiment of an optical structure 5in a plan view of the semiconductor chip. FIG. 8B illustrates the sideview in this respect. The optical structure 5 comprises structuredregions 5 a embodied as prisms. By way of example, the prisms can beetched into the semiconductor body.

The prisms are arranged parallel to one another. Furthermore, the prismsrun transversely with respect to the grating regions of the gratingstructure (not illustrated) and form therewith the angle α of greaterthan 0° and less than 90°, preferably of 45° (cf. FIG. 8A). The prismshave oblique side faces 11 (cf. FIG. 8B). These run at an angle β ofgreater than 0° and less than 90°, preferably of 45°, obliquely withrespect to a plane in which the grating structure extends.Advantageously, the polarization of the impinging radiation component S2can be rotated by reflection at two opposite side faces 11 of twoadjacent structured regions 5 a. In particular, the parallel polarizedradiation is converted into perpendicularly polarized radiation by theoptical structure 5.

It should be pointed out that the described exemplary embodiments of anoptical structure can in each case be combined with the differentexemplary embodiments of a grating structure. Furthermore, the inventionis not restricted by the description on the basis of the exemplaryembodiments. Rather, the invention encompasses any novel feature andalso any combination of features, which in particular includes anycombination of features in the patent claims, even if this feature orthis combination itself is not explicitly specified in the patent claimsor exemplary embodiments.

1-15. (canceled)
 16. A radiation-emitting semiconductor chip comprising:a semiconductor body comprising an active zone, which is configured toemit unpolarized radiation having a first radiation component of a firstpolarization and having a second radiation component of a secondpolarization; a grating structure, configured to act as a waveplate orpolarization filter and bring about an increase in one radiationcomponent relative to the other radiation component in the radiationemitted by the semiconductor chip through a coupling-out side, such thatduring operation the semiconductor chip emits polarized radiation havingthe polarization of the amplified radiation component, wherein theattenuated radiation component remains in the semiconductor chip; anoptical structure, configured to convert the polarization of at leastpart of the attenuated radiation component remaining in thesemiconductor chip into the polarization of the amplified radiationcomponent; and a reflective rear side situated opposite the coupling-outside.
 17. The radiation-emitting semiconductor chip according to claim16, wherein the grating structure comprises a plurality of alternatelyarranged first grating regions of a first material and second gratingregions of a second material, and wherein the grating regions of thesame material are at a distance from one another which is smaller than awavelength of the radiation generated by the active zone.
 18. Theradiation-emitting semiconductor chip according to claim 17, wherein thefirst and second grating regions are embodied in strip-type fashion andare arranged parallel to one another.
 19. The radiation-emittingsemiconductor chip according to claim 17, wherein the first or secondgrating regions of the grating structure acting as a waveplate areformed from a material that is transmissive to the radiation generatedin the active zone, wherein the material comprises Si0 ₂, GaAs, AlGaAs,InGaAlP or GaN.
 20. The radiation-emitting semiconductor chip accordingto claim 16, wherein the first radiation component experiences adifferent phase shift than the second radiation component upontransmission through the grating structure acting as a waveplate. 21.The radiation-emitting semiconductor chip according to claim 20, whereinthe grating structure acting as a waveplate is arranged between theactive zone and the reflective rear side of the semiconductor chip, andwherein a distance between the active zone and the reflective rear sideis set in such a way that, as a result of interference of radiation ofthe same polarization, one radiation component is amplified and theother radiation component is attenuated.
 22. The radiation-emittingsemiconductor chip according to claim 17, wherein the first gratingregions of the grating structure acting as a polarization filtercomprise a metal.
 23. The radiation-emitting semiconductor chipaccording to claim 22, wherein one radiation component is transmitted atthe grating structure acting as a polarization filter and the otherradiation component is reflected.
 24. The radiation-emittingsemiconductor chip according to claim 22, wherein the grating structureacting as a polarization filter is arranged on a surface of thesemiconductor body that is on the coupling-out side.
 25. Theradiation-emitting semiconductor chip according to claim 22, wherein thegrating structure is a contact structure for current spreading.
 26. Theradiation-emitting semiconductor chip according to claim 17, wherein theoptical structure comprises structured regions extending in a planearranged parallel to a plane in which the grating structure extends,wherein the structured regions run transversely with respect to thegrating regions and form with the latter an angle of greater than 0° andless than 90°.
 27. The radiation-emitting semiconductor chip accordingto claim 26, wherein the structured regions run transversely withrespect to the grating regions and form with the latter an angle of 45°.28. The radiation-emitting semiconductor chip according to claim 26,wherein the structured regions are arranged at least partly parallel toone another.
 29. The radiation-emitting semiconductor chip according toclaim 16, wherein the optical structure comprises structured regionshaving oblique side faces that run at an angle of greater than 0° andless than 90° obliquely with respect to a plane in which the gratingstructure extends.
 30. The radiation-emitting semiconductor chipaccording to claim 29, wherein the optical structure comprisesstructured regions having oblique side faces that run at an angle of 45°obliquely with respect to a plane in which the grating structureextends.
 31. The radiation-emitting semiconductor chip according toclaim 29, wherein the structured regions are embodied as prisms orpyramids.
 32. The radiation-emitting semiconductor chip according toclaim 16, wherein the reflective rear side is provided with the opticalstructure.
 33. A radiation-emitting semiconductor chip comprising: asemiconductor body comprising an active zone, which is configured toemit unpolarized radiation having a first radiation component of a firstpolarization and having a second radiation component of a secondpolarization; a grating structure, configured to act as a waveplate orpolarization filter and bring about an increase in one radiationcomponent relative to the other radiation component in the radiationemitted by the semiconductor chip through a coupling-out side, such thatduring operating the semiconductor chip emits polarized radiation havingthe polarization of the amplified radiation component, wherein theattenuated radiation component remains in the semiconductor chip; anoptical structure, configured to convert the polarization of at leastpart of the attenuated radiation component remaining in thesemiconductor chip into the polarization of the amplified radiationcomponent; and a reflective rear side situated opposite the coupling-outside, wherein the optical structure comprises structured regions havingoblique side faces that run at an angle of greater than 0° and less than90° obliquely with respect to a plane in which the grating structureextends.
 34. A radiation-emitting semiconductor chip comprising: asemiconductor body comprising an active zone, which is configured toemit unpolarized radiation having a first radiation component of a firstpolarization and having a second radiation component of a secondpolarization; a grating structure, configured to act as a waveplate andbring about an increase in one radiation component relative to the otherradiation component in the radiation emitted by the semiconductor chipthrough a coupling-out side, such that during operating thesemiconductor chip emits polarized radiation having the polarization ofthe amplified radiation component, wherein the attenuated radiationcomponent remains in the semiconductor chip; an optical structure,configured to convert the polarization of at least part of theattenuated radiation component remaining in the semiconductor chip intothe polarization of the amplified radiation component; and a reflectiverear side situated opposite the coupling-out side; wherein the gratingstructure acting as a waveplate is arranged between the active zone andthe reflective rear side of the semiconductor chip, and a distancebetween the active zone and the reflective rear side is set in such away that, as a result of interference of radiation of the samepolarization, one radiation component is amplified and the otherradiation component is attenuated.